/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_lattice_f32.c
*
* Description:	Processing function for the floating-point FIR Lattice filter.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @defgroup FIR_Lattice Finite Impulse Response (FIR) Lattice Filters
 *
 * This set of functions implements Finite Impulse Response (FIR) lattice filters
 * for Q15, Q31 and floating-point data types.  Lattice filters are used in a
 * variety of adaptive filter applications.  The filter structure is feedforward and
 * the net impulse response is finite length.
 * The functions operate on blocks
 * of input and output data and each call to the function processes
 * <code>blockSize</code> samples through the filter.  <code>pSrc</code> and
 * <code>pDst</code> point to input and output arrays containing <code>blockSize</code> values.
 *
 * \par Algorithm:
 * \image html FIRLattice.gif "Finite Impulse Response Lattice filter"
 * The following difference equation is implemented:
 * <pre>
 *    f0[n] = g0[n] = x[n]
 *    fm[n] = fm-1[n] + km * gm-1[n-1] for m = 1, 2, ...M
 *    gm[n] = km * fm-1[n] + gm-1[n-1] for m = 1, 2, ...M
 *    y[n] = fM[n]
 * </pre>
 * \par
 * <code>pCoeffs</code> points to tha array of reflection coefficients of size <code>numStages</code>.
 * Reflection Coefficients are stored in the following order.
 * \par
 * <pre>
 *    {k1, k2, ..., kM}
 * </pre>
 * where M is number of stages
 * \par
 * <code>pState</code> points to a state array of size <code>numStages</code>.
 * The state variables (g values) hold previous inputs and are stored in the following order.
 * <pre>
 *    {g0[n], g1[n], g2[n] ...gM-1[n]}
 * </pre>
 * The state variables are updated after each block of data is processed; the coefficients are untouched.
 * \par Instance Structure
 * The coefficients and state variables for a filter are stored together in an instance data structure.
 * A separate instance structure must be defined for each filter.
 * Coefficient arrays may be shared among several instances while state variable arrays cannot be shared.
 * There are separate instance structure declarations for each of the 3 supported data types.
 *
 * \par Initialization Functions
 * There is also an associated initialization function for each data type.
 * The initialization function performs the following operations:
 * - Sets the values of the internal structure fields.
 * - Zeros out the values in the state buffer.
 *
 * \par
 * Use of the initialization function is optional.
 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
 * To place an instance structure into a const data section, the instance structure must be manually initialized.
 * Set the values in the state buffer to zeros and then manually initialize the instance structure as follows:
 * <pre>
 *arm_fir_lattice_instance_f32 S = {numStages, pState, pCoeffs};
 *arm_fir_lattice_instance_q31 S = {numStages, pState, pCoeffs};
 *arm_fir_lattice_instance_q15 S = {numStages, pState, pCoeffs};
 * </pre>
 * \par
 * where <code>numStages</code> is the number of stages in the filter; <code>pState</code> is the address of the state buffer;
 * <code>pCoeffs</code> is the address of the coefficient buffer.
 * \par Fixed-Point Behavior
 * Care must be taken when using the fixed-point versions of the FIR Lattice filter functions.
 * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
 * Refer to the function specific documentation below for usage guidelines.
 */

/**
 * @addtogroup FIR_Lattice
 * @{
 */


/**
 * @brief Processing function for the floating-point FIR lattice filter.
 * @param[in]  *S        points to an instance of the floating-point FIR lattice structure.
 * @param[in]  *pSrc     points to the block of input data.
 * @param[out] *pDst     points to the block of output data
 * @param[in]  blockSize number of samples to process.
 * @return none.
 */

void arm_fir_lattice_f32(
    const arm_fir_lattice_instance_f32* S,
    float32_t* pSrc,
    float32_t* pDst,
    uint32_t blockSize)
{
	float32_t* pState;                             /* State pointer */
	float32_t* pCoeffs = S->pCoeffs;               /* Coefficient pointer */
	float32_t* px;                                 /* temporary state pointer */
	float32_t* pk;                                 /* temporary coefficient pointer */


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	float32_t fcurr1, fnext1, gcurr1, gnext1;      /* temporary variables for first sample in loop unrolling */
	float32_t fcurr2, fnext2, gnext2;              /* temporary variables for second sample in loop unrolling */
	float32_t fcurr3, fnext3, gnext3;              /* temporary variables for third sample in loop unrolling */
	float32_t fcurr4, fnext4, gnext4;              /* temporary variables for fourth sample in loop unrolling */
	uint32_t numStages = S->numStages;             /* Number of stages in the filter */
	uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

	gcurr1 = 0.0f;
	pState = &S->pState[0];

	blkCnt = blockSize >> 2;

	/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
	   a second loop below computes the remaining 1 to 3 samples. */
	while(blkCnt > 0u) {

		/* Read two samples from input buffer */
		/* f0(n) = x(n) */
		fcurr1 = *pSrc++;
		fcurr2 = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* Read g0(n-1) from state */
		gcurr1 = *px;

		/* Process first sample for first tap */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext1 = fcurr1 + ((*pk) * gcurr1);
		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext1 = (fcurr1 * (*pk)) + gcurr1;

		/* Process second sample for first tap */
		/* for sample 2 processing */
		fnext2 = fcurr2 + ((*pk) * fcurr1);
		gnext2 = (fcurr2 * (*pk)) + fcurr1;

		/* Read next two samples from input buffer */
		/* f0(n+2) = x(n+2) */
		fcurr3 = *pSrc++;
		fcurr4 = *pSrc++;

		/* Copy only last input samples into the state buffer
		   which will be used for next four samples processing */
		*px++ = fcurr4;

		/* Process third sample for first tap */
		fnext3 = fcurr3 + ((*pk) * fcurr2);
		gnext3 = (fcurr3 * (*pk)) + fcurr2;

		/* Process fourth sample for first tap */
		fnext4 = fcurr4 + ((*pk) * fcurr3);
		gnext4 = (fcurr4 * (*pk++)) + fcurr3;

		/* Update of f values for next coefficient set processing */
		fcurr1 = fnext1;
		fcurr2 = fnext2;
		fcurr3 = fnext3;
		fcurr4 = fnext4;

		/* Loop unrolling.  Process 4 taps at a time . */
		stageCnt = (numStages - 1u) >> 2u;

		/* Loop over the number of taps.  Unroll by a factor of 4.
		 ** Repeat until we've computed numStages-3 coefficients. */

		/* Process 2nd, 3rd, 4th and 5th taps ... here */
		while(stageCnt > 0u) {
			/* Read g1(n-1), g3(n-1) .... from state */
			gcurr1 = *px;

			/* save g1(n) in state buffer */
			*px++ = gnext4;

			/* Process first sample for 2nd, 6th .. tap */
			/* Sample processing for K2, K6.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext1 = fcurr1 + ((*pk) * gcurr1);
			/* Process second sample for 2nd, 6th .. tap */
			/* for sample 2 processing */
			fnext2 = fcurr2 + ((*pk) * gnext1);
			/* Process third sample for 2nd, 6th .. tap */
			fnext3 = fcurr3 + ((*pk) * gnext2);
			/* Process fourth sample for 2nd, 6th .. tap */
			fnext4 = fcurr4 + ((*pk) * gnext3);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			/* Calculation of state values for next stage */
			gnext4 = (fcurr4 * (*pk)) + gnext3;
			gnext3 = (fcurr3 * (*pk)) + gnext2;
			gnext2 = (fcurr2 * (*pk)) + gnext1;
			gnext1 = (fcurr1 * (*pk++)) + gcurr1;


			/* Read g2(n-1), g4(n-1) .... from state */
			gcurr1 = *px;

			/* save g2(n) in state buffer */
			*px++ = gnext4;

			/* Sample processing for K3, K7.... */
			/* Process first sample for 3rd, 7th .. tap */
			/* f3(n) = f2(n) +  K3 * g2(n-1) */
			fcurr1 = fnext1 + ((*pk) * gcurr1);
			/* Process second sample for 3rd, 7th .. tap */
			fcurr2 = fnext2 + ((*pk) * gnext1);
			/* Process third sample for 3rd, 7th .. tap */
			fcurr3 = fnext3 + ((*pk) * gnext2);
			/* Process fourth sample for 3rd, 7th .. tap */
			fcurr4 = fnext4 + ((*pk) * gnext3);

			/* Calculation of state values for next stage */
			/* g3(n) = f2(n) * K3  +  g2(n-1) */
			gnext4 = (fnext4 * (*pk)) + gnext3;
			gnext3 = (fnext3 * (*pk)) + gnext2;
			gnext2 = (fnext2 * (*pk)) + gnext1;
			gnext1 = (fnext1 * (*pk++)) + gcurr1;


			/* Read g1(n-1), g3(n-1) .... from state */
			gcurr1 = *px;

			/* save g3(n) in state buffer */
			*px++ = gnext4;

			/* Sample processing for K4, K8.... */
			/* Process first sample for 4th, 8th .. tap */
			/* f4(n) = f3(n) +  K4 * g3(n-1) */
			fnext1 = fcurr1 + ((*pk) * gcurr1);
			/* Process second sample for 4th, 8th .. tap */
			/* for sample 2 processing */
			fnext2 = fcurr2 + ((*pk) * gnext1);
			/* Process third sample for 4th, 8th .. tap */
			fnext3 = fcurr3 + ((*pk) * gnext2);
			/* Process fourth sample for 4th, 8th .. tap */
			fnext4 = fcurr4 + ((*pk) * gnext3);

			/* g4(n) = f3(n) * K4  +  g3(n-1) */
			/* Calculation of state values for next stage */
			gnext4 = (fcurr4 * (*pk)) + gnext3;
			gnext3 = (fcurr3 * (*pk)) + gnext2;
			gnext2 = (fcurr2 * (*pk)) + gnext1;
			gnext1 = (fcurr1 * (*pk++)) + gcurr1;

			/* Read g2(n-1), g4(n-1) .... from state */
			gcurr1 = *px;

			/* save g4(n) in state buffer */
			*px++ = gnext4;

			/* Sample processing for K5, K9.... */
			/* Process first sample for 5th, 9th .. tap */
			/* f5(n) = f4(n) +  K5 * g4(n-1) */
			fcurr1 = fnext1 + ((*pk) * gcurr1);
			/* Process second sample for 5th, 9th .. tap */
			fcurr2 = fnext2 + ((*pk) * gnext1);
			/* Process third sample for 5th, 9th .. tap */
			fcurr3 = fnext3 + ((*pk) * gnext2);
			/* Process fourth sample for 5th, 9th .. tap */
			fcurr4 = fnext4 + ((*pk) * gnext3);

			/* Calculation of state values for next stage */
			/* g5(n) = f4(n) * K5  +  g4(n-1) */
			gnext4 = (fnext4 * (*pk)) + gnext3;
			gnext3 = (fnext3 * (*pk)) + gnext2;
			gnext2 = (fnext2 * (*pk)) + gnext1;
			gnext1 = (fnext1 * (*pk++)) + gcurr1;

			stageCnt--;
		}

		/* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
		stageCnt = (numStages - 1u) % 0x4u;

		while(stageCnt > 0u) {
			gcurr1 = *px;

			/* save g value in state buffer */
			*px++ = gnext4;

			/* Process four samples for last three taps here */
			fnext1 = fcurr1 + ((*pk) * gcurr1);
			fnext2 = fcurr2 + ((*pk) * gnext1);
			fnext3 = fcurr3 + ((*pk) * gnext2);
			fnext4 = fcurr4 + ((*pk) * gnext3);

			/* g1(n) = f0(n) * K1  +  g0(n-1) */
			gnext4 = (fcurr4 * (*pk)) + gnext3;
			gnext3 = (fcurr3 * (*pk)) + gnext2;
			gnext2 = (fcurr2 * (*pk)) + gnext1;
			gnext1 = (fcurr1 * (*pk++)) + gcurr1;

			/* Update of f values for next coefficient set processing */
			fcurr1 = fnext1;
			fcurr2 = fnext2;
			fcurr3 = fnext3;
			fcurr4 = fnext4;

			stageCnt--;

		}

		/* The results in the 4 accumulators, store in the destination buffer. */
		/* y(n) = fN(n) */
		*pDst++ = fcurr1;
		*pDst++ = fcurr2;
		*pDst++ = fcurr3;
		*pDst++ = fcurr4;

		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurr1 = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* read g2(n) from state buffer */
		gcurr1 = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext1 = fcurr1 + ((*pk) * gcurr1);
		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext1 = (fcurr1 * (*pk++)) + gcurr1;

		/* save g1(n) in state buffer */
		*px++ = fcurr1;

		/* f1(n) is saved in fcurr1
		   for next stage processing */
		fcurr1 = fnext1;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {
			/* read g2(n) from state buffer */
			gcurr1 = *px;

			/* save g1(n) in state buffer */
			*px++ = gnext1;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext1 = fcurr1 + ((*pk) * gcurr1);
			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext1 = (fcurr1 * (*pk++)) + gcurr1;

			/* f1(n) is saved in fcurr1
			   for next stage processing */
			fcurr1 = fnext1;

			stageCnt--;

		}

		/* y(n) = fN(n) */
		*pDst++ = fcurr1;

		blkCnt--;

	}

#else

	/* Run the below code for Cortex-M0 */

	float32_t fcurr, fnext, gcurr, gnext;          /* temporary variables */
	uint32_t numStages = S->numStages;             /* Length of the filter */
	uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

	pState = &S->pState[0];

	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurr = *pSrc++;

		/* Initialize coeff pointer */
		pk = pCoeffs;

		/* Initialize state pointer */
		px = pState;

		/* read g0(n-1) from state buffer */
		gcurr = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext = fcurr + ((*pk) * gcurr);
		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext = (fcurr * (*pk++)) + gcurr;

		/* save f0(n) in state buffer */
		*px++ = fcurr;

		/* f1(n) is saved in fcurr
		   for next stage processing */
		fcurr = fnext;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {
			/* read g2(n) from state buffer */
			gcurr = *px;

			/* save g1(n) in state buffer */
			*px++ = gnext;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext = fcurr + ((*pk) * gcurr);
			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext = (fcurr * (*pk++)) + gcurr;

			/* f1(n) is saved in fcurr1
			   for next stage processing */
			fcurr = fnext;

			stageCnt--;

		}

		/* y(n) = fN(n) */
		*pDst++ = fcurr;

		blkCnt--;

	}

#endif /*   #ifndef ARM_MATH_CM0 */

}

/**
 * @} end of FIR_Lattice group
 */
